Add some tests.

tests/language/src/ListDoubleIndexInLoopTest.dart

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+// Dart test program for testing arrays.
+
+bar() => true;
+
+// The type propagation in Dart2Js wrongly took the intersection of all incoming
+// types in a loop-phi. In this case the back-edge brought type 'number' which,
+// combined with 'integer' (i = 0) was narrowed to 'integer'. As a result no

[Lasse Reichstein Nielsen, 2012/04/16 10:43:32]

What kind of type propagation is this? For optimization only?
Narrowing num to int seems like an unsafe analysis.

[floitsch, 2012/04/16 12:08:37]

Narrowing has uses too. In this case, of course, it's a bug. I will fix it.

+// check was inserted for the list access.
+foo(a) {
+  var i = 0;
+  while (true) {
+    if (i > 1) return a[i];
+    if (bar()) {
+      // Adding a double guarantees a double result. Therefore guard by an if.
+      i = i + 1.5;
+    }
+  }
+}
+
+main() {
+  Expect.throws(() => foo([1, 2]));
+}